Multiplexed gear actuation system for a dual clutch transmission

ABSTRACT

A gear actuation mechanism for an automatic transmission, comprising: a motor; first and second gear actuation shafts; means of selecting one power path from each of two sets of power paths in response to rotation of the first and second actuation shafts, respectively; and means of alternately driveably connecting the motor to either the first gear actuation shaft or the second gear actuation shaft.

BACKGROUND OF THE INVENTION

This invention is in the field of gear actuation mechanisms forautomatic transmissions. The invention is particularly suited for gearactuation of dual clutch automatic transmissions.

In a dual clutch automatic transmission, it is necessary to select atmost one even gear and at most one odd gear at any particular time. Formaximum operational flexibility, it is desirable for the choices of oddgear and even gear to be independent.

Typically, this is accomplished by providing two independent gearactuation mechanisms, including two motors. The motors and associatedcircuitry account for a substantial fraction of the costs of theactuation systems. Therefore, it is desirable to have one motor ratherthan two.

A well know actuation system uses a single motor to turn a single drumwhich actuates both even and odd gears. However, that system does notallow even and odd gears to be selected independently. For example, whensixth gear is selected, the only odd gears available would be fifth orseventh. Third gear cannot be selected, so a direct shift from sixthgear to third gear is impossible.

This invention uses a planetary gear set to multiplex a single motor,such that the motor is alternately connected to one of two independentdrums. One drum actuates the odd gears and the other actuates the evengears. Although only one drum may be moved at a time, all positions oneach drum are available independent of the position of the other drum.

Furthermore, the invention takes advantage of the relationship betweenthe clutch state and the need to change gears to determine which of thetwo drums should be driven by the motor. Specifically, the odd gear isnever changed while driving in an odd gear and the even gear is neverchanged while driving in an even gear. Therefore, the motor drives theeven drum whenever the odd clutch is engaged and drives the odd drumwhenever the even clutch is engaged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an end view of a first embodiment of the gear actuationmechanism.

FIG. 2 is a sectional view through section A-A in FIG. 1.

FIG. 3 is a sectional view through section B-B in FIG. 1.

FIG. 4 is a sectional view through section C-C in FIG. 1.

FIG. 5 is an end view of a second embodiment of the gear actuationmechanism.

FIG. 6 is a schematic representation of a typical dual clutchtransmission.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is an actuation system for a dual clutchtransmission or transaxle. Before describing the actuation system indetail, the general structure and operation of a typical dual clutchtransmission will be described.

FIG. 6 illustrates the structure of a typical rear wheel drive dualclutch transmission. Front wheel drive dual clutch transaxles havesimilar structure and operation, except that the output shaft is on adifferent axis from the input shaft. In this document, the term“transmission” should be understood to include both rear wheel drivetransmissions and transverse mounted transaxles. Input shaft 100 isdriven by the vehicle engine. Output shaft 102 drives the vehiclewheels, preferably via a differential. Clutch 110 connects input shaft100 to the odd gear intermediate shaft 104 whenever the clutch isapplied and disconnects them whenever the clutch is disengaged.Similarly, clutch 112 connects input shaft 100 to the even gearintermediate shaft 106 whenever the clutch is applied and disconnectsthem whenever the clutch is disengaged. Even gear intermediate shaft 106is a hollow shaft that is concentric with odd gear intermediate shaft104.

Gears 126, 128, 130, 132, 134, and 136 provide several differentselectable power paths between the odd gear intermediate shaft 104 andcountershaft 108, each with a different speed ratio. One of the powerpaths is selected by moving synchronizers 150 and 152 to appropriatepositions. To engage first gear, synchronizer 150 is moved leftward tocouple gear 132 to shaft 108. To engage third gear, synchronizer 150 ismoved rightward to couple gear 134 to shaft 108. To engage seventh gear,synchronizer 152 is moved leftward to couple gear 130 to shaft 104.Gears 142 and 144 provide a continuously engaged power path fromcountershaft 108 to output shaft 102. Moving synchronizer 152 to theright engages fifth gear, which is a direct drive gear, by couplingshaft 104 to output shaft 102. When both synchronizers 150 and 152 arein the neutral position, no power flows between shaft 104 and shaft 102and no speed relationship is enforced.

Gears 114, 116, 118, 120, 122, and 124 provide several differentselectable forward gear power paths between the even gear intermediateshaft 106 and countershaft 108, each with a different speed ratio. Toengage second gear, synchronizer 148 is moved leftward to couple gear124 to shaft 108. To engage fourth gear, synchronizer 146 is movedrightward to couple gear 116 to shaft 106. To engage sixth gear,synchronizer 146 is moved leftward to couple gear 114 to shaft 106.Gears 138, 140, and an idler gear which is not shown provide aselectable reverse gear power path from even gear input shaft 106 tocountershaft 108. Moving synchronizer 148 to the right engages reverseby coupling gear 140 to shaft 108. When both synchronizers 146 and 148are in the neutral position, no power flows between shaft 106 and shaft102 and no speed relationship is enforced.

To prepare the vehicle for a launch from stationary in a forwarddirection, first gear is selected as described above and both clutchesare set at zero torque capacity. In response to accelerator pedalmovement, clutch 110 is gradually engaged. Launch in reverse is similar,except that reverse gear is selected and clutch 112 is graduallyengaged.

Whenever the vehicle is moving in an odd numbered gear, clutch 110 willbe engaged and power will flow via one of the odd power paths to theoutput shaft. Clutch 112 will be disengaged and no power flows throughany of the even power paths. To prepare for a shift into an evennumbered gear, synchronizers 146 and 148 are positioned to select thedesired gear as described above. Then, clutch 112 is gradually engagedwhile clutch 110 is gradually disengaged, transferring the power flow tothe even gear power path. Similarly, a shift from an even gear to an oddgear is accomplished by selecting the odd gear while all power flowsthrough an even power path and then gradually engaging clutch 110 whilegradually disengaging clutch 112.

The present invention provides a mechanism for adjusting the positionsof synchronizers or other couplers to engage the desired power paths.FIG. 1 is an end view of a first embodiment of the gear actuationmechanism. FIG. 2 is a sectional view through section A-A in FIG. 1. Aplanetary gear set includes a sun gear 14, a ring gear 16, a planetcarrier 18, and a set of planet gears 20. The planet gears are supportedfor rotation by the planet carrier and mesh with the sun gear and ringgear. The sun gear and planet gears each have 12 external teeth and thering gear has 36 internal teeth. A gear actuator motor 10 drives sungear 14 via shaft 12. Carrier 18 has 24 external teeth which mesh withthe 36 external gear teeth of gear 22. When ring gear 16 is heldstationary, each revolution of motor 10 results in ¼ revolution ofcarrier 18 and ⅙ revolution of gear 22.

Gear 22 is connected to the even actuator drum 26 by actuation shaft 24.Even actuator drum 26 has two grooves 28 and 30 with the axial locationof the grooves varying along the circumference of the drum. A fork (notshown) extends into groove 28 and positions synchronizer 146. Anotherfork extends into groove 30 and positions synchronizer 148. Therotational position of the drum determines the positions of the forksand synchronizers. The axial location of each groove around thecircumference is selected such that particular positions of the drumcorrespond to each desired odd gear state.

Ring gear 16 has 36 external teeth which mesh with the 24 gear teeth ofgear 32. Gear 32 is connected to gear 34 which has 12 teeth. Gear 34meshes with gear 36 which has 36 teeth. When carrier 18 is heldstationary, each revolution of motor 10 results in ⅓ revolution of ringgear 16, ½ revolution of gears 32 and 34, and ⅙ revolution of gear 36.Gear 36 is connected by actuation shaft 38 to odd actuator drum 40. Drum40 has two grooves, 42 and 44, which guide forks that determine thepositions of synchronizers 150 and 152.

The remainder of the mechanism functions to hold either ring gear 16 orplanet carrier 18 stationary. Motor 10 may then be used to adjust theposition of either drum 26 or drum 40, depending upon which element isheld. In a first embodiment, the selection of which element to holdstationary is determined by the states of the clutches.

Motor 64 drives shaft 66 which moves trolley 68 left or right.Translation of trolley 68 adjusts the torque capacity of clutch 110through a mechanism which is not illustrated. Examples of such amechanisms can be found in U.S. Pat. Nos. 6,679,362 and 7,073,649. Thetorque capacity is zero at the position shown and increases as thetrolley is moved to the right. There is some additional travel availableto the left of this position which is used to select which drum will berotated by motor 10. Similarly, motor 50 drives shaft 52 which movestrolley 54 left or right. Trolley 54 is shown at the rightmost limit ofits travel. As it is moved to the left, the first portion of its travelis used to select which drum will be rotated by motor 10 and theremainder or the travel is used to control the torque capacity of clutch112.

Linkages 72 and 58 are supported for rotation about pin 60. Pin 70attached to trolley 68 engages groove 74 causing linkage 72 to rotateabout pin 60 as the trolley is moved. Similarly, pin 56 engages groove62 causing linkage 58 to rotate as trolley 54 moves. Grooves 74 and 62are L-shaped such that the movement of the linkages occurs while thetrolleys move through the first portion of their travel and the linkagesare stationary during the torque capacity adjustment portion of thetravel.

FIGS. 3 and 4 are sectional views through sections B-B and C-C in FIG.1, respectively. Pins 78 and 82 are supported by the transmission case76. When trolley 68 is in the torque capacity adjustment portion of itstravel, linkage 72 moves to the position illustrated in FIG. 3. Aninclined surface on linkage 72 pushes pin 78 into one of a set of holes48 in gear 36. These holes 48 are positioned to correspond to desiredodd gear states such as first, third, fifth, seventh, and neutral. Whentrolley 68 is moved to the leftmost stop, linkage 72 rotates such thatpin 78 is pushed out of the hole by spring 80, allowing gear 36 torotate. Similarly, when trolley 54 is at the rightmost position of itstravel, linkage 58 moves to the position shown in FIG. 4. In thisposition, the linkage allows spring 84 to push pin 82 away from gear 22.Whenever trolley 54 is moved into the torque capacity adjusting portionof its travel, the inclined surface on linkage 58 pushes pin 82 into oneof a set of holes 46 in gear 22. These holes correspond to desired evengear states second, fourth, sixth, reverse, and neutral. An addedfeature of this mechanism is that the clutch is mechanically precludedfrom engaging whenever the corresponding drum is not in a positionassociated with a well defined gear state.

A skilled mechanism designer would be able to create a number ofalternate mechanical linkages between the clutch actuators and the gearactuation shafts to satisfy the function of holding the gear actuationshaft stationary whenever the corresponding clutch is applied. Any suchmechanism should be considered an equivalent to the correspondingmechanism described above.

To prepare the transmission for a forward launch, motor 64 is engaged tomove trolley 68 all the way to the left stop and motor 50 is engaged tomove trolley 54 to the beginning of the torque capacity adjustmentportion of its travel. In this configuration, gear 22 and planet carrier18 are held stationary. Then, motor 10 is engaged to rotate drum 40 tothe position corresponding to first gear. Once thus configured, motor 64is used to adjust the torque capacity of clutch 110 in response to theaccelerator pedal position.

When the vehicle is driving in an odd gear, the transmission is preparedfor a shift into an even gear by engaging motor 50 to position trolley54 at its stop. In this configuration, gears 36, 34, 32, and ring gear16 are held stationary. Motor 10 is then engaged to move drum 22 to theposition corresponding to the desired even gear. To complete the shift,motors 50 and 64 are used in a coordinated fashion to gradually increasethe torque capacity of clutch 112 while decreasing the torque capacityof clutch 110. Similarly, to prepare for a shift into an odd numberedgear, trolley 68 is moved all the way to the left stop and then motor 10is engaged to select the desired odd gear.

In a second embodiment, which is depicted in FIG. 5, the selection ofwhich element to hold stationary is determined by an independent controlsignal. In response to this independent control signal, solenoid 86moves pin 88 left or right. When pin 88 is moved to the right, asdepicted, gear 22 in held stationary and motor 10 is used to move drum40. When pin 88 is moved to the left, gear 36 is held stationary andmotor 10 is used to move drum 26. Alternatively, the control signalcould be hydraulic as opposed to electrical in which case pin 88 wouldbe driven by a piston.

1. A gear actuation mechanism for a multiple speed automatictransmission, comprising: a motor (10); first (38) and second (24) gearactuation shafts; means of engaging and releasing couplers within thetransmission in response to rotation of the first and second gearactuation shafts; a configurable mechanism driveably connecting themotor alternately to the first gear actuation shaft or the second gearactuation shaft.
 2. The gear actuation mechanism of claim 1, wherein theconfigurable mechanism comprises an epicyclic gearing assembly withfirst (14), second (18), and third (16) elements rotating about a commonaxis such that the speed of the second element is constrained to be aweighted average of the speeds of the first and third elements.
 3. Thegear actuation mechanism of claim 2, wherein the epicyclic gearingassembly is a planetary gear set comprising: a sun gear (14); a ringgear (16); a planet carrier (18); and a set of planet gears (20)supported for rotation with respect to the planet carrier and eachmeshing with both the sun gear and the ring gear.
 4. The gear actuationmechanism of claim 2, wherein the motor (10), the first gear actuationshaft (38), and the second gear actuation shaft (24) are each driveablyconnected to a different one of the first (14), second (18), and third(16) elements.
 5. The gear actuation mechanism of claim 4, furthercomprising: a means (86 and 88) of alternately holding either the firstgear actuation shaft (38) or the second gear actuation shaft (24)against rotation in response to a control signal.
 6. The gear actuationmechanism of claim 4, wherein the multispeed automatic transmission is adual clutch transmission comprising first (110) and second (112)clutches.
 7. The gear actuation mechanism of claim 6, furthercomprising: a mechanism holding the first gear actuation shaft (38)against rotation whenever the first clutch (110) is partially or fullyengaged; and a mechanism holding the second gear actuation shaft (24)against rotation whenever the second clutch (112) is partially or fullyengaged.
 8. A gear actuation mechanism for a dual clutch automatictransmission, said dual clutch automatic transmission comprising: aninput shaft (100); an output shaft (102); first (104) and second (106)intermediate shafts; first (110) and second (112) clutches releaseablydriveably connecting the input shaft (100) to the first intermediateshaft (104) and second intermediate shaft (106), respectively; and afirst and second set of selectable power paths from the firstintermediate shaft and second intermediate shaft, respectively, to theoutput shaft; and wherein the gear actuation mechanism comprises: amotor (10); first (38) and second (24) gear actuation shafts; means ofselecting at most one power path from the first set of power paths andat most one power path from the second set of power paths in response torotation of the first and second gear actuation shafts, respectively;means of releaseably driveably connecting the motor selectively toeither one of the first gear actuation shaft or second gear actuationshaft.
 9. The gear actuation mechanism of claim 8, wherein the means ofselecting one power path from the first set of power paths comprises: afirst drum (40) attached to the first gear actuation shaft (38) andhaving one or more circumferential grooves (42 and 44); a first set ofshift forks, each with a follower located in one of the grooves in thefirst drum such that the fork moves in response to rotation of the firstdrum; and a first set of couplers (150 and 152) which connect anddisconnect gears and shafts in response to movement of the first shiftforks.
 10. The gear actuation mechanism of claim 9, wherein the means ofselecting one power path from the second set of power paths comprises: asecond drum (26) attached to the second gear actuation shaft (24) andhaving one or more circumferential grooves (28 and 30); a second set ofshift forks, each with a follower located in one of the grooves in thesecond drum such that the fork moves in response to rotation of thesecond drum; and a second set of couplers (146 and 148) which connectand disconnect gears and shafts in response to movement of the secondshift forks.
 11. The gear actuation mechanism of claim 8, furthercomprising an epicyclic gearing assembly with first (14), second (18),and third (16) elements rotating about a common axis such that the speedof the second element is constrained to be a weighted average of thespeeds of the first and third elements.
 12. The gear actuation mechanismof claim 11, wherein the epicyclic gearing assembly is a planetary gearset comprising: a sun gear (14); a ring gear (16); a planet carrier(18); and a set of planet gears (20) supported for rotation with respectto the planet carrier and each meshing with both the sun gear and thering gear.
 13. The gear actuation mechanism of claim 11, wherein themotor (10), the first gear actuation shaft (38), and the second gearactuation shaft (38) are each driveably connected to a different one ofthe first (14), second(18), and third (16) elements.
 14. The gearactuation mechanism of claim 13, further comprising: a means (86 and 88)of alternately holding either the first gear actuation shaft or thesecond gear actuation shaft against rotation in response to a controlsignal.
 15. The gear actuation mechanism of claim 13, wherein: the firstgear actuation shaft (38) is held against rotation whenever the firstclutch (110) is partially or fully engaged; and the second gearactuation shaft (24) is held against rotation whenever the second clutch(112) is partially or fully engaged.
 16. The gear actuation mechanism ofclaim 15, wherein the first and second clutches, respectively, areprecluded from being engaged whenever the corresponding gear actuationshaft is not in one of a predefined set of acceptable positions.
 17. Adual clutch automatic transmission comprising: first (110) and second(112) clutches; a first set of selectable power paths, each includingthe first clutch (110); a second set of selectable power paths, eachincluding the second clutch (112); a motor (10); first (38) and second(24) gear actuation shafts; a means of engaging the couplers (150 or152) of one power path from the first set of power paths in response torotation of the first gear actuation shaft (38); a means of engaging thecouplers (146 or 148) of one power path from the second set of powerpaths in response to rotation of the second gear actuation shaft; and aconfigurable mechanism driveably connecting the motor (10) alternatelyto the first gear actuation shaft (38) or the second gear actuationshaft (24).
 18. The dual clutch automatic transmission of claim 17,wherein the configurable mechanism comprises an epicyclic gearingassembly with a first element (18) driveably connected to the first gearactuation shaft (38), a second element (16) driveably connected to thesecond gear actuation shaft (24), and a third element (14) driveablyconnected to the motor (10), and wherein the speed of one of the threeelements (18) is constrained to be the weighted average of the speeds ofthe other two elements (14 and 16).
 19. The dual clutch automatictransmission of claim 18, further comprising a means (86 and 88) ofholding one of the two gear actuation shafts against rotation inresponse to a control signal.
 20. The dual clutch automatic transmissionof claim 18, wherein: the first gear actuation shaft (38) is heldagainst rotation whenever the first clutch (110) is partially or fullyengaged; and the second gear actuation shaft (24) is held againstrotation whenever the second clutch (112) is partially or fully engaged.